(a) Field of the Invention
This invention relates to methods for purification of paclitaxel from paclitaxel-containing material.
(b) Description of the Related Art
Paclitaxel is the most important antineoplastic agent for ovarian cancer, breast cancer, etc. discovered in the United States in the 1960's when the National Cancer Institute began a large-scale screening program for selecting material having anti-cancer activity. Paclitaxel has been widely used as an antineoplastic agent since approval by the FDA (Federal Drug & Food Agency) in 1992.
Because paclitaxel is isolated and purified from the bark of Yew trees in which paclitaxel is present in a very low amount (about 0.02%), a high cost in purification of paclitaxel has been demanded, and destruction of nature and ecosystems has been provoked. To overcome the above problems, a method for semi-synthesis of paclitaxel using precursors obtained from the needles of Yew trees and a method for large scale production using a Yew tree-cell culturing method have been developed. The prior arts relating to methods of purification of paclitaxel are as follows.
The procedure of WO 00/40573 of Foo et al. provides a method for preparing a high purity paclitaxel from a paclitaxel-containing material, the method comprising: obtaining a low purity extract by a liquid/liquid extracting procedure; purifying the extract through a silica column; conducting precipitation of the extract with an acetone/aqueous solvent; and repeating the silica column and crystallization steps. However, this procedure needs performing of chromatography three times and of crystallizing two times to acquire high purity paclitaxel. In addition, a precipitation method using an acetone/aqueous solvent should be undertaken in this procedure, and productivity of Paclitaxel is 49–73%, which is very low.
The procedure of WO 00/078741 of Bui-khac et al. provides a method for the extraction and purification of paclitaxel that includes the steps of: a) extracting a raw material comprising paclitaxel with an organic solvent from the natural source of taxanes; b) treating the raw material with a base or acid to obtain a biomass by precipitation; c) percolorizing the biomass by removing resin and natural pigment contained therein; and d) chromatographically purifying at least once and crystallizing at least once by adding acetone and hexane. However, it is known that paclitaxel is decomposed to 10-deacetylpaclitaxel and baccatin III in an acidic or base condition. Therefore, this method has difficulty in purifying paclitaxel with a high yield, and needs much time because of complicated procedures.
The procedure of U.S. Pat. No. 5,900,367 of Hong et al. provides a method for mass production of paclitaxel. The steps include: a) synthetic absorbent treatment of a crude extract, prepared by a method of organic solvent extraction, to remove a tar component; b) addition of hexane to the filtrate to precipitate crude taxol; c) fractional precipitation of the crude taxol in a mixture of alcohol and water, and drying the precipitate to obtain taxol powder; and d) high performance liquid chromatography of the taxol powder. This method has an advantage in isolation and purification of high purity with a small quantity of solvent by using only three extracting and purifying solvents: dichloromethane, methanol, and hexane. However, there is a need for re-fractional precipitation of the filtrate recovered from precipitation solution to enhance purity and fractional precipitation yield.